1. Field of the Invention
The present invention generally relates to a technology for supplying power to a process circuit. The present invention specifically relates reducing power consumption of a process circuit.
2. Description of the Related Art
Recently, enhancement of server capacity is resulting in a significant rise in power consumption of servers. Especially, so called blade servers have higher central processing unit (CPU) density than the so called rack mount servers, so that the blade servers consume higher power. Therefore, in places such as the so called Internet Data Centers (IDC's), which includes many blade servers, a power layout is carried out to ensure that sufficient power is supplied.
However, recently, increasingly high performing CPU's are used in the servers and multiple such CPU's are mounted on a single server. Sometimes the required amount of power can exceed the estimated amount of power in the original power layout. To avoid this, it becomes necessary to restrict the number of servers mounted on a rack.
Japanese Patent Laid-Open Publication No. 2005-202506 discloses controlling power consumption of CPU's in a blade server with hardware called Blade Management Controller (BMC). Specifically, the BMC causes the CPU's to operate at lower operating frequencies than their original operating frequencies. When an operating frequency of a CPU is less, it requires lower power.
However, if an operating frequency of a CPU is reduced, the processing capacity of the CPU also drops. Therefore, if the operating frequencies of CPU's in a blade server are reduced, the processing capacity of the entire blade server drops.
Generally a load on a CPU in a typical server (CPU load) fluctuates with time. The CPU load instantaneously increases when the CPU executes a spike process, and CPU load reduces when a process performed by the CPU ends. FIG. 6 is a graph of CPU load against time of a CPU in a typical server. The CPU load increases to almost 100 percent when the CPU executes a spike process at a time t.
If the spike process is executed when the operating frequency of a CPU in a blade server has been intentionally reduced to save the power consumption of the CPU, it is obvious that the spike process disadvantageously continues for a longer time than when the CPU is operating at its original operating frequency.